DESCRIPTION: The universe of tobacco products is expanding, with new noncombustible products gaining popularity even as the reduction in prevalence of cigarette smoking slows or stalls. E-cigarettes, or Electronic Nicotine Delivery Systems (ENDS), are the most prevalent of these emerging noncombustible products. With sales increasing rapidly and more efficient pulmonary delivery devices under development, ENDS are likely to play an increasing role in the future tobacco market. Little is known about the cognitions and behaviors leading to or sustaining ENDS use. Smokers may use ENDS to subvert smoking restrictions (i.e. a bridge product), to reduce perceived smoking harms, or for cessation, possibly delaying use of proven treatments. With respect to daily ENDS users, the majority of information is limited to retrospective surveys and convenience samples of White males. Our research suggests Black smokers are less likely than White smokers to try or to use ENDS, perhaps due to a greater degree of perceived harm associated with ENDS, a preference for menthol, or cultural norms. However, with the recent purchase of Blue(c) e-cigarettes by Lorillard Tobacco Company (maker of Newport cigarettes), differential adoption of ENDS by race may not continue as the company markets mentholated ENDS to Black smokers. Thus, it is timely and critical to study how all smokers, including Blacks and menthol smokers, experience and initiate ENDS using valid, innovative research methods. Our research represents a first step towards understanding the immediate environmental contexts and psychological correlates associated with ENDS initiation in menthol and non-menthol smokers interested in trying ENDS. Our observational study features three weeks of concurrent ecological momentary assessment (EMA) and in-depth interview data collection, followed by a 30-day follow-up telephone contact to assess cigarette and ENDS use. We will enroll 100 daily cigarette smokers from the Washington, D.C. metro area. Since 80% of Black smokers prefer menthol cigarettes, the sample will be stratified into four groups (n=25 per group) by menthol use and race (non-Hispanic White and non-Hispanic Black), allowing us to disaggregate the influence of menthol preference from cultural norms/expectancies on ENDS initiation. Participants will use our preexisting EMA data collection system to collect data on tobacco use behaviors over the course of the three-week study. In Week 1, participants will collect baseline data on their usual smoking pattern. In Week 2, we will provide participants with a week's supply of ENDS and instructions to use the products at least three times daily. In Week 3, we will replenish participants' ENDS supply and encourage participants to use the products as they see fit. Participants will also take part in a semi-structured in-depth interview at the end of each week. Week 1 interviews will focus on a process evaluation of the EMA data collection experience, while the Week 2 and 3 interviews will focus on how ENDS-associated cognitions, expectancies and norms evolve with ENDS use and increasing familiarity with the product. Qualitative data from the interviews will complement the quantitative EMA data to examine the interplay between environment, cognitions, and behaviors driving ENDS initiation based on Social Cognitive Theory. Within-person aims will examine the longitudinal relationship between environmental context (e.g., location, presence of others), psychological state (e.g., mood), and tobacco dependence (e.g., craving) on an individual's ENDS use. Exploratory secondary aims include a between- person examination of the effects of race and menthol preference on ENDS initiation and will allow for exploration of interaction effects between the stratification variables by comparing our formative between-person EMA findings with between-case findings from in-depth interviews. This exploratory R21 will contribute to the emerging field of ENDS research by identifying potential mechanisms promoting ENDS initiation and predicting ENDS patterns of use, including whether ENDS displace or are used concurrently with cigarettes, or are used as aids to reduce harm or quit smoking. This study will be the first to examine ENDS use among Black and menthol smokers, two subpopulations of interest to the Center for Tobacco Products and tobacco control in general. The research will support a future R01 grant submission to more closely examine the causal pathways and long term behavioral outcomes following ENDS initiation.